That's exactly the point. I don't want to blast a hole in the rock and then
fill it up with concrete. I want to anchor the tower base to the rock with
only enough concrete to come a few inches above grade. My concerns are the
-How much up force will the anchors handle? There will be a lot of leverage
produced by the wind on the tower.
-How deep into the rock should I go? A few inches doesn't seem to be enough
given the winds and exposed location on top of the hill.
-The "T" base of the tower is drilled for three pairs of one inch bolts. Can
the holes in the rock be aligned accurately enough for the bolts to slide
through the base holes easily? If a pair of holes are drilled a few inches
apart will the rock between them still retain its strength?
-Normally, in concrete, J bolts are used and tied to the rebar in the
footing. I guess I would need longer threaded rods with whatever is used to
anchor them to the rock on the bottom end.
From: K7LXC@aol.com [mailto:K7LXC@aol.com]
Sent: Thursday, February 16, 2006 10:16 AM
To: firstname.lastname@example.org; email@example.com
Subject: Re: [TowerTalk] UST HDX589 crank-up tower base on rock?
In a message dated 2/13/2006 3:17:48 A.M. Pacific Standard Time,
> Hi TTians,
> In a few months I will be starting construction on a new house which
located on top of a hill on a adjacent piece of property. My HDX589 is
currently installed on the manufacturer's recommended base of 5x5x8.5
of concrete with rebar.
> Test holes in the vicinity of the new house have revealed between 16
inches of soil on top of the rock the hill is made of. A blasting
has told me that the stone is very strong and stable and he will not
any problems blasting for the house basement and foundation.
> I won't be able to dig another hole and use the same method as the
location. Instead, I have been told there are bolts or rods that can be
into holes drilled into the stone and epoxied in place which can support
> I will probably need an engineer but don't know where to begin to
familiar with this type of work or what alternatives exist. Anyone
with this technique or alternative method who can steer me in the right
direction? Any particulars I need to provide to him/her that I need to
research in advance?
Well, getting an engineer's blessing is always a good idea. Maybe
you can talk to a couple and get some off-the-record feedback on what you've
got and what's possible.
I would be in favor of using the rock as the base and then you only
have to use a little concrete to get the top of the base a little above
grade. Why would you dynamite out a bunch of rock and then fill in the hole
with concrete when the rock by itself would accomplish the same thing?
You can rent a rock corer to drill the appropriate holes for the
factory anchor bolts - or have someone come out and do it - and then you can
epoxy them in or use rock expansion bolts - or both. It'll be real strong.
TOWER TECH -
Professional tower services for amateurs
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